1. Field
The present embodiments relate to position sensors and, more particularly, to position sensors for detecting a position of an object in multiple dimensions.
2. Brief Description of Related Developments
A number of methods exist for determining the position of a moving object. For example, there are vehicle guidance systems that use radar signals that interact with stripes on a roadway to determine the position of an automobile. Other position systems utilize wireless radio communications. However, both of these systems require a source of power to be available on the moving object. The radio waves are also subject to degradation from intervening structures and electrical signals.
Position may also be determined by, for example a linear variable differential transformer (LVDT) is a displacement transducer which utilizes a single primary and two secondary windings wound around a cylindrical bobbin. A movable nickel-iron core or armature is positioned inside the windings and the movement of the core is measured to obtain the position of the movable object. Hall effect sensors may be used in a similar manner to measure displacement. Generally LVDTs and Hall effect sensors are used to measure finite displacements such as the displacement of linear actuators and pistons.
For high precision positioning systems such as steppers, suspension and/or scanning stages and the like, conventional methods of position measurement use capacitive, inductive, optical and laser sensors. These sensors generally provide high resolution coupled with low positioning noise. However, the overall cost, limitations in travel range and desired number of degrees of freedom narrow the field of their applications.
By way of example, in conventional feedback devices employing periodic signals, such as sine and cosine signals, that are produced by the sensors are routed to an analog to digital converter (ADC) of, for example, a motor controller where the signals are processed in the digital domain for determining the position of an object. However, the sine/cosine period and ADC resolution may not be sufficient to produce the desired position resolution for certain applications that demand a high degree of position resolution.
It would be advantageous to be able to determine both two dimensional position and gap width measurements using the same sensors and magnets for both measurements. It would also be advantageous to provide a cost effective, high resolution absolute encoder. It would be further advantageous to increase the resolution of a position feedback device from a base resolution of a motor controller and/or encoder.